Generally, plastic bottles, as typified by PET bottles, are widely known as a container to be filled with beverages such as juices and soft drinks. Plastic bottles, when used, have to have predetermined strength to maintain their shape. Meanwhile, used empty plastic bottles are sometimes disposed, collection and recycling is preferable.
To efficiently collect used bottles, it is desirable that the bottles are collapsible and the collapsed bottles do not take up much space. Particularly, if consumers can easily collapse the bottles, the burden on the consumers when recycling the bottles can be reduced. Moreover, with such easily collapsible bottles, if a consumer collapses the bottle to put it into a collection box later and keeps the thus collapsed bottle in his/her bag, that bottle does not take up much space in the bag, so the handiness of used bottles can be improved.
As an example of those collapsible bottles, the bottle disclosed in JP 3,108,377 is well known. That bottle has an accordion-like structure formed with a large number of concave grooves in the longitudinal direction of the bottle. By collapsing the bottle horizontally to contract the accordion-like structure, the volume in the bottle can be reduced.
However, the plastic bottle disclosed in JP 3,108,377 is not so versatile, so it needs further improvement.